A roof may have a steep-slope or a low-slope. Traditional tabbed or laminated shingles are typically used for steep-slope roofing applications. Traditional tabbed or laminated shingles are referred to as “water-shedding” products. That is, water that falls on a shingle on an upper portion of the roof runs down the shingle and onto an underlying, next lower shingle. The water runs down the shingles, until the water reaches the bottom of the steep roof.
As the slope of a roof decreases, more emphasis is placed on the need for waterproofing the roof covering, because less aid to physical movement of water is provided by the slope of the roof. Residential and commercial products are available for low-slope roofing applications. Most products used in residential low-slope roofing applications include two or more plies or layers to enhance long-term performance. A typical low-slope roofing product may have one or more underlayment or base sheets and a separate cap sheet. Typically, the separate cap sheets are similar to typical asphalt roofing shingles and may include a woven or non-woven fiber mat that is coated on both upper and lower surfaces with asphalt. The separate cap sheet may have a layer of roofing granules on the upper surface that is configured to match the roofing shingles of a nearby steep-slope roof. One or both of the base sheet and the separate cap sheet may be self-adhering.
Many low-slope roofing products used in commercial applications are non-asphalt based membranes that are installed on a low-slope roof using a variety of attachment means, such as with cold or hot applied adhesive materials, or with mechanical fasteners. The seams between portions of the membrane may be heat welded or glued. Typical commercial membranes are manufactured in solid colors, commonly white or black, and may be limestone covered. Other known low-slope roofing products include membranes with patterns printed on the visible surface, and membranes coated with paint or a reflective coating.